There was no clear evidence to suggest that phosphorus had significantly more impact on yield of one variety than another.

Application of 7.2 lbs P with the seed significantly improved grain yield by 6.4 bushels compared to the control (0 lbs P), and by 4.2 bushels compared to 12 lbs P applied by broadcasting.

Yield improved by 4.9 bushels with 24 lbs P broadcast and incorporated, compared to the control.

Meanwhile, yield differences were not significant between the control and 12 lbs rate, and between 12 and 24 lbs P rates.

Crop vigor was assessed 42 days after planting, by measuring light reflectance (NDVI) from the crop canopy of each plot using the GreenSeeker sensor.

The most vigorous treatments were at P = 7.2 lbs seed applied, and 24 lbs broadcast and incorporated.

Conclusion

In-furrow application of starter phosphorus at one third the recommended broadcast rate produced the highest yields. This is consistent with the in-furrow recommended rate of phosphorus as a percentage of the broadcast rate for yield optimization in the current growing season.